Rotary piston internal combustion engine

ABSTRACT

A rotary piston engine has two pistons mounted in two communicating housings. The pistons are disposed in the order of 180* out of phase and the eccentrics for the housings are slightly offset from each other to improve the positioning of the communicating ducting between the housings.

United States Patent 1 [111 3,782,337

Feller Jan. 1, 1974 ROTARY PISTON INTERNAL [56] References Cited COMBUSTION ENGINE UNITED STATES PATENTS [75] Inventor: Fritz Feller, Crewe, England 3,236,213 2/l966 Yokoi et a1. /15 [73] Assigneez The secretary of State for Defense, 3,371,654 3/1968 Garslde 60/15 X London England Primary ExaminerA1 Lawrence Smith [22] Filed: Aug. 30, 1971 Assistant Examiner-Michae1 Koczo, Jr.

Appl. No.: 176,059

Foreign Application Priority Data Sept. 1, 1970 Great Britain 41,709/

U.S. Cl. l23/8.05 Int. Cl. F021) 53/00 Field of Search 123/8.43, 8.29, 8.05;

AttorneyCushman, Darby & Cushman ABSTRACT A rotary piston engine has two pistons mounted in two communicating housings. The pistons are disposed in the order of out of phase and the eccentrics for the housings are slightly offset from each other to im prove the positioning of the communicating ducting between the housings.

6 Claims, 5 Drawing Figures PATENTEU H974 3,782,337

' sum 1 [IF 2 Inventor FQ/ rz @115? Y B data, acme PATENTEB JAN 1 I974 suwenrg Inventor ROTARY PISTON INTERNAL COMBUSTION ENGINE This invention concerns a rotary piston internal combustion engine and is concerned with improvements in the rotary piston engine described in our prior U.K. Patent No. 1,008,745.

In U.K. Patent No. 1,008,745 there is described a rotary piston internal combustion engine comprising first and second rotary pistons which are respectively mounted within first and second cavities of a housing or housings so as to define first and second sets of working chambers therewith,.each cavity and its respective piston having n and n l lobes, the second piston and its cavity being substantially larger than the first piston and its cavity, means for producing planetary rotation of the first and second pistons in their cavities and substantially in phase with each other, means for supplying air to the second working chambers, means for permitting the withdrawal of exhaust gases therefrom, a first duct for transferring air which has been compressed in the second working chambers to the first working chambers for further compression therein, a second duct for transferring combustion gases which have been partially expanded in the first working chambers to the second working chambers for further expansion therein, and means for supplying fuel to the first working chambers, the first working chambers and second working chambers varying in volume and position during the rotation of the pistons, so that a working cycle is effected and the arrangement being such that communication via a said duct starts to become established between the respective first and second working chambers when one said chamber is substantially at its maximum volume and the other said chamber is simultaneously substantially at its minimum volume, and ceases to be established substantially when the said one chamber has reached its minimum volume and the said other chamber is simultaneously at its maximum volume.

According to one aspect of the present invention there is provided a rotary piston internal combustion engine comprising first and second rotary pistons which are respectively mounted within first and second cavities of a housing or housings so as to define first and second sets of working chambers therewith, each cavity and its respective piston being trochoidal and respectively having n and n 1 lobes, the second piston and its cavity being substantially larger than the first piston and its cavity, means for producing planetary rotation of the first and second pistons at the same rotational speed in their cavities, means for supplying air to the second working chambers, means for permitting the withdrawal of exhaust gases therefrom, a first duct transferring air which has been compressed in the second working chambers to the first working chambers for further compression therein, a second duct for transferring combustion gases which have been partially expanded in the first working chambers to the second working chambers for further expansion therein, and means for supplying fuel to the first working chambers, the first and second working chambers varying in volume and position during the rotation of the pistons so that a working cycle is efiected, and the arrangement being such that communication via a said duct starts to become established between the respective first and second working chambers when one said chamber is substantially at its maximum volume and the other said chamber is simultaneously substantially at its minimum volume, and ceases to be established substantially when the said one chamber has reached its minimum volume and the said other chamber is simultaneously at its maximum volume, the first and second pistons being out of phase with each other.

In this specification the term the pistons are in phase with each other means that pistons are simultaneously in the same angular positions and the term the pistons are out of phase with each other means that the pistons are not simultaneously in the same angular positions.

Preferably the pistons are arranged on eccentrics which are between substantially and substantially 210 out of phase with each other.

The pistons may be arranged on eccentrics which are in the order of substantially 180 out of phase with each other, but preferably with the eccentrics for the second piston, leads the eccentrics for the first piston by 210.

In some positions of the second piston, the number of second working chambers may exceed the number of first working chambers by at least one.

The profile of the inner surface of each said cavity is preferably that of a two-lobed epitrochoid, the profile of the peripheral surface of each said piston being substantially that of the three-lobed inner envelope of the two-lobed epitrochoid,

There may be three first working chambers, there being four second working chambers in certain predetermined positions of the second piston.

The peripheral surface ofthe first piston may have circumferentially spaced recesses therein so that preferred combustion shapes and volumes and preferred compression ratios can be achieved.

According to a further feature of the present invention a plane through the minor axis and the polar axis of the first cavity is substantially parallel to a plane through the minor axis and the polar axis of the second cavity.

A two-lobed epitrochoid has a substantially oval shape, and by minor axis, we mean the smallest diameter of the substantially oval shape.

Preferably a plane through the polar axes of both the first and second cavities cuts the plane through the minor axis and the polar axis of either the first or second cavities at an angle of up to substantially l0.

Preferably the angle is substantially 5.

Further features of the invention will become apparent from the folowing description of embodiments of the invention given merely byway of example in which:

FIG. 1 is a diagrammatic view of a rotary piston internal combustion engine according to one aspect of the present invention and,

FIGS. 2 5 illustrate the operation of the engine of FIG. 1.

Referring first to FIG. 1, a rotary piston internal combustion engine has two rotary pistons 10,11 which are respectively mounted on separately eccentric shafts 12,13. The eccentric shafts 12,13 are constrained to run in the order of 180 out of phase and at the same speed by means which are not shown, which may be constituted by gears, by a number of connecting rods running on eccentrics by chains, or by any other suitable means. The pistons 10,11 are respectively rotatable in a planetary manner in cavities 14,15 formed in a stationary housing 9, the pistons being adapted to be rotated 180 out of phase with each other in the direction of the arrows 8.

The minor axes 50,51 of the cavities l4 and 15 are offset and parallel to each other. The line 52 joining the polar axes 53 and 54 cuts the minor axes 50 and 51 at substantially 5.

The pistons 10,11 have peripheral surfaces which includes three circumferentially spaced apex portions a,11a respectively, which are symmetrically arranged with respect to the axes of the pistons 10,11. The apex portions 10a, 11d have sealing edges 10!), 11b respectively parallel to the shafts 12,13 and which are at all times sealing engagement with the peripheral surfaces of the cavities 14,15 respectively. The peripheral surfaces of the cavities 14,15 include two circumferentially spaced arched lobe defining portions 14a, 15a respectively which are successively joined together and which provide, at their junctions 21,22 and 16,17 points of minimum distance from the shafts 12,13. Thus the peripheral surface of the cavities 14,15 are substantially those of a two-lobed epitrochoid. The peripheral surfaces of the pistons 10,11 are substantially those of the three-lobed inner envelope of the twolobed epitrochoid.

The piston 11, which is larger than the piston 10, and which is in sealing engagement with the cavity 15 at points 16,17 defines with its cavity 15 either four or five of the working chambers A,B,C,D,E, according to the position of the piston 11. These working chambers may, if desired be sealed from each other in known manner by sealing strips (not shown) at each of the three apex portions 11b of the piston 11. Additionally, the sides of the piston 11 may be provided with further sealing strips (not shown) which connect with the sealing strips at the apex portions 11b. Sealing strips, not shown, which are similar to the sealing strips at the apex portions 11b may also be slidably mounted at the said junctions 16,17.

The piston 10, which is smaller than the piston 11, has recesses or depressions 18,19,20 which are provided in the peripheral surface of the piston 10 and are circumferentially spaced apart. The piston 10, with its recesses 18,19,20 forms with its cavity 14 three working chambers F,G,H. The working chambers F,G,H, may be sealed from each other in a manner generally similar to that in which the working chambers A,B,C,D,E are sealed from each other, except that it is not necessary to provide slidably mounted sealing strips at the said junctions 21,22. It is, of course, by reason of the lack of such sealing strips at the said junctions 21,22 that the piston 10 forms with its cavity 14 only three working chambers F,G,H whereas the piston 11 forms with its cavity 14 either four or five of the working chambers A-E.

Air may enter the engine through an inlet port 23., exhaust gases leaving the engine from an exhaust port 24. A transfer duct permits air to flow from the cavity 15 to the cavity 14, while a transfer duct 26 permits combustion gases to flow from the cavity 14 to the cavity 15.

A fuel injector 27 is arranged at position 29 in the wall of the cavity 14, opposite the side thereof where the transfer ducts 25 and 26 are situated. The fueld injector 27 thus supplies fuel to the working chamber G. A further fuel injector may be arranged in the wall of the cavity 14 near the fuel injector 27.The fuel may be ignited by means of a spark plug arranged in the wall of the cavity 14 adjacent to the injector 27, preferably downstream of the injector 27. If two injectors are provided two spark plugs may be provided. The use of such external means of ignition as spark plugs however may not in all cases be necessary and reliance may be placed merely on compression ignition. This engine preferably operates solely on the compression ignition cycle.

The various working chambers A-H vary in both volume and position during the rotation of the pistons 10,11 so that a working cycle is efiected in which the air entering the cavities 14,15 is compressed and the combustion gases therein are expanded.

The nature of said working cycle will be apparent from an examination of FIGS. 2-5 of the drawings. Thus, as will be seen from the reference numerals 1,Il,IlI,lV the working chamber communicating with the inlet port 23 is of successively increasing volume as the rotors 10,11 rotate in the direction of the arrows, 8. A suction stroke is thus provided in which air is sucked through the inlet port 23. t

The air which has been so sucked through the inlet port 23 is first subjected to a low pressure compression stage, indicated by the reference numerals V-Vll and is thereafter subjected to a high pressure compression stage, indicated by the reference numerals Vlll. During the low pressure compression stage, some of the air being compressed is within the cavity 15 whilst some of it is within the cavity 14. At the end of the low pressure compression stage, all the air being compressed is within the cavity 14. It will therefore be appreciated that the air received by the cavity 14 has been precompressed in passing through the cavity.

Combustion takes place when the air has been compressed to the volume indicated by the reference numeral 1X (see FIG. 2).

Thereafter expansion proceeds in two stages, a high pressure stage indicated by the reference numerals X-Xl, and a low pressure stage indicated by the reference numerals XII-X111. It will be noted that the high pressure expansion stage, indicated by the reference numerals X-XI, occurs substantially wholly within the cavity 14, whilst the low pressure expansion stage indicated by the reference numerals XII-X111. It will be noted that the high pressure expansion stage, indicated by the reference numerals X-XI, occurs substantially wholly within the cavity 14, whilst the low pressure expansion stage indicated by the reference numerals X11- -XII1, occurs partly within cavity 14 and partly within the cavity 14. Thus, it 15. be appreciated that, after the combustion gases have been partially expanded within the cavity 14, they are expanded yet further within the cavities 14 and 15.

The exhaust stroke is represented by the decreasing volume indicated by the reference numerals XlV-XVI.

It will be noted that the communication, via the transfer duct 25, starts to become established between the working chambers B, F, when the working chamber B is substantially at its maximum volume and the working chamber F is substantially at its minimum volume, and ceases to be established when the working chamber B is substantially at its minimum volume and the working chamber F is simultaneously substantially at its maximum volume.

Similarly, communication via the transfer duct 26 starts to become established between the working chambers 11,!) when the chamber H is substantially at its maximum volume and the chamber D is simultaneously substantially at its minimum volume, and ceases to be established substantially when the chamber H has reached its minimum volume and the chamber D is simultaneously substantially at its maximum volume.

The engine has the following transfer port timing:

LP inlet transfer port 25 opens 306 BTDCLP HP inlet transfer port 25 closes l7l BTDC HP HP exhaust transfer port 26 opens 203 ATDC HP LP exhaust transfer port 26 closes 330 ATDC.HP

BTDC means Before top dead centre ATDC means After top dead centre LP means Low Pressure HP means High Pressure Top dead centre in a rotary piston engine is when apex of the piston is pointing vertically downwards when viewed in the drawings and when the eccentric on its particular eccentric shaft is in its uppermost position. The angles referred to are eccentric shaft angles.

The edges of the ports are marked, AA, BB, CC, DD, EE, PF, 66, HH, II, J], 14K and LL.

Further port timing details are as follows:

AA 249 BTDC LP Inlet port 23 starts to close at maximum summated inlet volume, i.e. when the total volume of the LP and HP chambers receiving a new charge is at a maximum. Charge momentum prevents blow-back before edge BB is reached by the rotor apex. The function is the same as that of the normal reciprocating piston engine inlet valve.

BB 189 BTDC LP Inlet port 23 closes. This position is determined by port size and shape.

CC 306 BTDC LP LP inlet transfer port 25 opens before maximum LP volume is reached to allow HP filling, but as lateas possible to reduce dead loss volume in LP when the gas transfer is completed. It is also late to prevent exhaust gas blow down from the HP exhaust transfer port 26.

DD 274 BTDC LP LP inlet transfer port 25 closes. This position depends on the port shape and size.

EE 213 BTDC HP HP inlet transfer port 25 starts to close. This position is determined from FF and depends upon port size and shape.

HP inlet transfer port 25 closes before HP exhaust transfer port 26 opens to prevent contamination of the transferred charge and to allow time for exhaust scavenging. It closes late to suit the position of the LP inlet transfer port 25 and thus minimise transfer passage length. The pressure of the remaining charge in LPTDC chamber helps to prevent exhaust gas carryover.

GG 203 ATDC HP HP exhaust transfer port 26 opens as late as possible to reduce percentage losses in the exhaust transfer passage 26 and to delay opening until FF is closed. It should also coincide with minimum LP volume while retaining a short exhaust transfer passage.

HH 238 ATDC HP HP exhaust transfer port closes.

II 303 ATDC LP LP exhaust transfer port starts to open.

.1] 330 ATDC LP LP exhaust port opened at minimum summated. volume around the exhaust transfer passage. The increasing LP volume provides good initial HP exhaust scavenging prior to the next secondary scavenging stage.

It should also be positioned to give a short exhaust transfer passage.

KK 195 ATDC LP LP exhaust port 24 opens 50 before maximum sumated expansion volume. This early opening matches the time required for gas acceleration to facilitate exhaust as with a reciprocating piston engine exhaust valve.

LL 255 ATDC LP LP Exhaust port 24 fully open.

While actual angles have been quoted we are by no means restricting ourselves to such angles as obviously these can readilybe varied. It is envisaged that these angles may be varied by up to i 25.

By arranging the eccentric shafts for the pistons out of phase and particularly substantially 180 out of phase from each other has enabled the transfer ducts 25 and 26 to have an improved positioning in respect of engine timing and has also enabled the ducts to have a shorter length and hence a smaller volume. The shapes of the ports where the transfer ducts communicate with the chambers, also improved for greater efficiency.

By arranging the minor axes 'of the cavities out of line has also helped in arranging the transfer ducts in positions where they provide improved timing characteristics.

The engine of the present invention could incorporate a plurality of the pistons 10 and a corresponding plurality of the pistons 11 in the same way as a reciprocating engine may be provided with a plurality of cylinders. Alternatively in such a case a single piston 11 may provide for the pre-compression of the air and final expansion of the exhaust gases of a plurality of the pistons 10.

I claim:

1. A rotary piston internal combustion engine comprising a housing, said housing having first and second cavities closely adjacent one another, a first rotary piston mounted in said first cavity to define a first set of working chambers therewith,'a second rotary piston mounted in said second cavity to define a second set of working chambers therewith, each cavity and its respective piston being trochoidal in shape and respectively having n and n+1 lobes, each cavity having a major, a minor, and a polar axis, said two cavities being arranged adjacent to each other with their major axes substantially parallel to each other, means for producing planetary rotation of said first and second pistons at the same rotational speed in said cavities, a first duct for transferring compressed air from said second set of working chambers to said first set of working chambers for further compression therein, a second duct for transferring combustion gases which have been partially expanded in said first set of working chambers to said second set of working chambers for further expansion therein, means for rendering the length of said first and second ducts approximately the same and for aligning said first and second ducts to communicate with said cavities with a small oblique angle therebetween, said means including a plane through said minor axis and said polar axis of said first cavity being arranged substantially parallel to and offset from a plane through said minor axis and said polar axis of said second cavity wherein said first duct and said second duct communicate with the peripheries of said cavities and are at a less oblique angle and are shorter than if said minor axis of said first and second Cavities were in line, means for supplying air to said second set of working chambers for compression therein, means for permitting the withdrawal of exhaust gases from said second set of working chambers, means for supplying fuel to said first set of working chambers, said first and second sets of working chambers varying in volume and position during the rotation of said pistons so that a working cycle is effected, the arrangement being such that communication via said duct starts to become established between the respective first and second sets of working chambers when one of said chambers if substantially at its maximum volume and the other of said chambers is simultaneously at its minimum volume, and ceases to be established substantially when the said one chamber has reached its minimum volume and the other chamber is simultaneously at its maximum volume, said means for producing planetary rotation of said first and second pistons being out of phase with each other.

2. A rotary piston internal combustion engine as claimed in claim 1 wherein a plane through said polar axes of both said first and second cavities cuts said planes through said minor axes and said polar axes of said cavities at an angle of up to substantially 10.

3, A rotary piston internal combustion engine is claimed in claim 2 wherein said angle is substantially 5 4. A rotary piston internal combustion engine as claimed in claim 1 in which said means for producing planetary rotation of said first and second pistons are eccentric shafts arranged between substantially and substantially 210 out of phase with each other.

5. A rotary piston internal combustion engine as claimed in claim 4 in which said eccentric shafts are arranged substantially in the order of 180 out of phase with each other.

6. A rotary piston internal 7 combustion engine as claimed in claim 4 in which said eccentric shaft for said second piston leads said eccentric shaft for said first piston in the order of 210. 

1. A rotary piston internal combustion engine comprising a housing, said housing having first and second cavities closely adjacent one another, a first rotary piston mounted in said first cavity to define a first set of working chambers therewith, a second rotary piston mounted in said second cavity to define a second set of working chambers therewith, each cavity and its respective piston being trochoidal in shape and respectively hAving n and n+1 lobes, each cavity having a major, a minor, and a polar axis, said two cavities being arranged adjacent to each other with their major axes substantially parallel to each other, means for producing planetary rotation of said first and second pistons at the same rotational speed in said cavities, a first duct for transferring compressed air from said second set of working chambers to said first set of working chambers for further compression therein, a second duct for transferring combustion gases which have been partially expanded in said first set of working chambers to said second set of working chambers for further expansion therein, means for rendering the length of said first and second ducts approximately the same and for aligning said first and second ducts to communicate with said cavities with a small oblique angle therebetween, said means including a plane through said minor axis and said polar axis of said first cavity being arranged substantially parallel to and offset from a plane through said minor axis and said polar axis of said second cavity wherein said first duct and said second duct communicate with the peripheries of said cavities and are at a less oblique angle and are shorter than if said minor axis of said first and second cavities were in line, means for supplying air to said second set of working chambers for compression therein, means for permitting the withdrawal of exhaust gases from said second set of working chambers, means for supplying fuel to said first set of working chambers, said first and second sets of working chambers varying in volume and position during the rotation of said pistons so that a working cycle is effected, the arrangement being such that communication via said duct starts to become established between the respective first and second sets of working chambers when one of said chambers if substantially at its maximum volume and the other of said chambers is simultaneously at its minimum volume, and ceases to be established substantially when the said one chamber has reached its minimum volume and the other chamber is simultaneously at its maximum volume, said means for producing planetary rotation of said first and second pistons being out of phase with each other.
 2. A rotary piston internal combustion engine as claimed in claim 1 wherein a plane through said polar axes of both said first and second cavities cuts said planes through said minor axes and said polar axes of said cavities at an angle of up to substantially 10*.
 3. A rotary piston internal combustion engine as claimed in claim 2 wherein said angle is substantially 5*.
 4. A rotary piston internal combustion engine as claimed in claim 1 in which said means for producing planetary rotation of said first and second pistons are eccentric shafts arranged between substantially 150* and substantially 210* out of phase with each other.
 5. A rotary piston internal combustion engine as claimed in claim 4 in which said eccentric shafts are arranged substantially in the order of 180* out of phase with each other.
 6. A rotary piston internal combustion engine as claimed in claim 4 in which said eccentric shaft for said second piston leads said eccentric shaft for said first piston in the order of 210*. 